Inherent scatter in pool boiling critical heat flux on reference surfaces

Evaluating boiling heat transfer enhancement depends on reliable reference values in the form of boiling curves and critical heat flux (CHF) values. Typically, the evaluation is performed in pool boiling conditions with water at atmospheric pressure. Literature includes a wide scatter in reference values, prompting this study to comprehensively evaluate boiling performance and CHF on reference surfaces to investigate the scatter's origin and set a definitive reference value. The study recorded 125 boiling curves and CHF values on nominally identical bare copper surfaces, establishing an average boiling curve and mean CHF value. Despite consistent experimental conditions, the recorded CHF values displayed significant variability with a mean CHF of 1112 ± 102 kW m−2 and a scatter from 902 kW m−2 (−19 % of average CHF) to 1339 kW m−2 (+25 % of average CHF). Using Rohsenow's correlation on the average boiling curve, a Csf factor of 0.0151 was obtained. The acquired CHF data is proposed to serve as a foundational benchmark for future research in enhancing pool boiling heat transfer.